test if rmarkdown format is rdocx_document similar to knitr::is_html_output()

Question

Depending on format output, I want all plots in rmarkdown to be a certain size if the output is word (officedown::rdocx_document:) and a different size if the output is html (bookdown::html_document2:).

I was thinking this could be achieved by having two chunks at the start where only one is evaluated if the output is the one I want, something like this test.Rmd file:

---
title: "test"
output:
  bookdown::html_document2:
  officedown::rdocx_document:
always_allow_html: true 
---


```{r setup, include = FALSE}
library(tidyverse)
```

```{r htmltest, include = FALSE, eval = knitr::is_html_output()}
#if output if html, run this:
knitr::opts_chunk$set(echo = TRUE, fig.width = 10, fig.height = 8)
```


```{r wordtest, include = FALSE, eval = knitr::is_latex_output()}
#if output if rdocx_document, run this:
knitr::opts_chunk$set(echo = TRUE, fig.width = 5, fig.height = 5)
```


# plot1

```{r plot, include = TRUE, echo = FALSE, eval = TRUE}

iris %>% 
  ggplot(aes(x = Petal.Length, y = Sepal.Width)) +
  geom_line()

```

# plot2 
```{r plot2, include = TRUE, echo = FALSE, eval = TRUE}

iris %>% 
  ggplot(aes(x = Petal.Width, y = Sepal.Width)) +
  geom_line()

```

# end

For the case of the html, the following render call works:

rmarkdown::render('test.Rmd', output_format = "html_document2")

but for the officedown::rdocx_document: call, it doesn't work:

rmarkdown::render('test.Rmd', output_format = "rdocx_document")

This is to be expected as I test for knitr::is_latex_output() in the code.

What is the equivalent of knitr::is_latex_output() or knitr::is_html_output() for officedown::rdocx_document:?

This solution mentions that for word, you can run include=knitr::pandoc_to("docx") but I have tried that and it didn't work (I think its because its for standard word output word_document: and not officedown::rdocx_document:)

Any suggestions (or comments on the approach I'm taking)?

thanks

edit

When I run and render using the following as @stefan suggested:

```{r wordtest, include = FALSE, eval = knitr::pandoc_to("docx")}
#if output if rdocx_document, run this:
knitr::opts_chunk$set(echo = TRUE, fig.width = 5, fig.height = 5)
```

I get the following Error: pandoc document conversion failed with error 1. I don't get this when I render the html format.

sessionInfo()
R version 4.2.1 (2022-06-23 ucrt)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 19045)

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
 [1] lubridate_1.9.2  forcats_1.0.0    stringr_1.5.0    dplyr_1.1.2      purrr_1.0.1      readr_2.1.4      tidyr_1.3.0      tibble_3.2.1     ggplot2_3.4.2    tidyverse_2.0.0  officer_0.6.3    flextable_0.9.4  officedown_0.3.1 bookdown_0.37    rmarkdown_2.25 


pandoc_version()
[1] ‘3.1.1’